The effects of ultrasound and heat pretreatments on ethanol yields from cassava chips were investigated.
Cassava slurries were sonicated for 10 and 30 s at the amplitudes of 80, 160, and 320 lmpp (peak to peak
amplitude in lm) corresponding to low, medium, and high power levels, respectively. The sonicated and
non-sonicated (control) samples were then subjected to simultaneous liquefaction-saccharification and
ethanol fermentation. Cassava starch-to-ethanol conversion efficiencies showed that higher ethanol
yields were directly related to sonication times, but not to power levels. Significantly higher ethanol
yields were observed only for sonicated samples at the high power level. The ethanol yield from the sonicated
sample was 2.7-fold higher than yield from the control sample. Starch-to-ethanol conversion rates
from sonicated cassava chips were also significantly higher; the fermentation time could be reduced by
nearly 24 h for sonicated samples to achieve the same ethanol yield as control samples. Thus, ultrasound
pretreatment enhanced both the overall ethanol yield and fermentation rate. When compared to heattreated
samples, the sonicated samples produced nearly 29% more ethanol yield. Combined heat and
ultrasound treatment had no significant effect on overall ethanol yields from cassava chips. Ultrasound
is also preferable to heat pretreatment because of lower energy requirements, as indicated by energy balances.
Integration of ultrasound application in cassava-based ethanol plants can significantly improve
ethanol yields and reduce the overall production costs.